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The normal boiling point of a certain liquid X is 130.9 °C, but when 19.9 g of urea (NH2) CO are dissolved in 200. g of X, it is found that
Question
The normal boiling point of a certain liquid X is 130.9 °C, but when 19.9 g of urea (NH2) CO are dissolved in 200. g of X, it is found that the solution boils at 134.1 °C instead. Use this information to calculate the molal boiling point elevation constant K, of X. Be sure your answer has the correct number of significant digits x 1 ℃.mol -kg
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2021-07-18T23:47:12+00:00
2021-07-18T23:47:12+00:00 1 Answers
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Answer:
K = 1.93 °C/m
Explanation:
This question can be solved by formula of elevation of boiling point.
Boiling T° of solution – Boiling T° of pure solvent = K . m . i
Our solute is urea.
Our solvent is X.
We convert mass of urea to moles: 19.9 g . 1 mol / 60.06g = 0.331 mol
We convert g of solute to kg = 200 g . 1 kg/ 1000g = 0.2kg
m = molality → moles of solute / kg of solvent
m = 0.331 mol / 0.2 kg = 1.66 m
As urea is an organic compound, no ions will be formed.
i = 1 (a non ionizing compound)
Let’s replace data in formula:
134,1°C – 130.9°C = K . 1.66 m . 1
3.2 °C / 1.66 m = K
K = 1.93 °C/m